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Purpose To determine the test-retest reproducibility of neurochemical concentrations obtained with a highly optimized, short-echo, single-voxel proton MR spectroscopy (MRS) pulse sequence at 3T and 7T using state-of-the-art hardware. Methods A semi-LASER sequence (echo time = 26-28 ms) was used to acquire spectra from the posterior cingulate and cerebellum at 3T and 7T from six healthy volunteers who were scanned four times weekly on both scanners. Spectra were quantified with LCModel. Results More neurochemicals were quantified with mean Cramér-Rao lower bounds (CRLBs) ≤20% at 7T than at 3T despite comparable frequency-domain signal-to-noise ratio. Whereas CRLBs were lower at 7T ( P < 0.05), between-session coefficients of variance (CVs) were comparable at the two fields with 64 transients. Five metabolites were quantified with between-session CVs ≤5% at both fields. Analysis of subspectra showed that a minimum achievable CV was reached with a lower number of transients at 7T for multiple metabolites and that between-session CVs were lower at 7T than at 3T with fewer than 64 transients. Conclusion State-of-the-art MRS methodology allows excellent reproducibility for many metabolites with 5-min data averaging on clinical 3T hardware. Sensitivity and resolution advantages at 7T are important for weakly represented metabolites, short acquisitions, and small volumes of interest. Magn Reson Med 76:1083-1091, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Muscle 1H magnetic resonance spectroscopy noninvasively measures intramyocellular lipid levels, which correlate with obesity, insulin resistance, and type 2 diabetes. The appearance of muscle magnetic resonance spectra is influenced by bulk magnetic susceptibility and residual dipolar couplings which depend on the angle between the muscle fibers and the main magnetic field. This study used a 4 T magnet to examine the influence of foot orientation on the appearance and quantification of muscle magnetic resonance spectra from the soleus and the vastus lateralis. For each individual, intramyocellular lipid, extramyocellular lipid, and creatine concentrations were quantified in the soleus and the vastus lateralis during one session. Foot orientation was found to influence the appearance of muscle spectra from the soleus but not from the vastus lateralis. It was concluded that quantifying intramyocellular lipid by the standard LCModel using a water reference may be more appropriate than using a creatine reference in the presence of residual dipolar couplings. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]